Electron tube having a photoelectron confining mechanism

Abstract

This invention relates to an electron tube having a structure for enabling a stable operation for a long time. In the electron tube, at least a confining mechanism is arranged between a photocathode and the electron incident surface of a semiconductor device, which are arranged to oppose each other. In the arrangement, the area of the opening of the confining mechanism is at least equal to or smaller than that of the electron incident surface, thereby confining the orbits of photoelectrons from the photocathode. This structure avoids bombardment of electrons arriving at portions other than the electron incident surface of the semiconductor device and prevents the semiconductor device from being unnecessarily charged.

What is claimed is:  
     
       1. An electron tube comprising: 
       a photocathode provided so as to emit photoelectrons in correspondence with incident light;  
       a semiconductor device having an electron incident surface for receiving the photoelectrons from said photocathode, said semiconductor device being arranged such that its electron incident surface faces said photocathode; and  
       a confining mechanism provided between said photocathode and said semiconductor device so as to confine a spread of the photoelectrons from said photocathode, said confining mechanism having an, opening for passing through the photoelectrons from said photocathode toward said electron incident surface,  
       wherein said opening of said confining mechanism has an area not greater than that of said electron incident surface of said semiconductor device.  
     
     
       2. A tube according to claim  1 , further comprising: 
       a container being a hollow member which has a first opening and a second opening opposing said first opening, said photocathode provided on the first opening side of said container; and  
       a stem provided an the second opening side of said container so as to define a distance between said photocathode and said electron incident surface.  
     
     
       3. A tube according to claim  1 , further comprising an envelope having an opening for supporting said photocathode at a predetermined position and accommodating said confining mechanism such that said semiconductor device is positioned between said confining mechanism and an inner bottom surface of said envelope. 
     
     
       4. A tube according to claim  1 , further comprising: 
       a cathode electrode provided so as to apply a predetermined voltage to said photocathode; and  
       an anode electrode provided between said photocathode and said semiconductor device, said anode electrode having a first surface facing said photocathode, a second surface opposing said first surface, and a through hole extending from said first surface to said second surface; and  
       wherein said confining mechanism includes said anode electrode, and said opening of said confining mechanism is defined by a second-surface-side opening of said through hole of said anode electrode.  
     
     
       5. A tube according to claim  4 , further comprising a mesh electrode provided in the through hole of said anode electrode. 
     
     
       6. A tube according to claim  4 , wherein said anode electrode has a collimator portion which extends from said first surface to said photocathode while surrounding a first-surface-side opening of said through hole of said anode electrode. 
     
     
       7. A tube according to claim  1 , further comprising: 
       a cathode electrode provided so as to apply a predetermined voltage to said photocathode;  
       an anode electrode provided between said photocathode and said semiconductor device, said anode electrode having a through hole for passing through the photoelectrons from said photocathode toward said electron incident surface of said semiconductor device; and  
       a collimator electrode supported by said anode electrode, said collimator electrode having a third surface lacing said photocathode, a fourth surface opposing said third surface, and a through hole extending from said third surface to said fourth surface; and  
       wherein said confining mechanism includes said collimator electrode, and said opening of said confining mechanism is defined by a fourth-surface-side opening of said through bole of said collimator electrode.  
     
     
       8. A tube according to claim  1 , wherein said semiconductor device has an n-type substrate and a p-type semiconductor layer formed on said n-type semiconductor substrate and having said electron incident surface. 
     
     
       9. An electron tube comprising: 
       a photocathode provided so as to emit photoelectrons in correspondence with incident light;  
       a semiconductor device having an electron incident surface for receiving the photoelectrons from said photocathode and an incident surface electrode having an opening which dees said electron incident surface, said semiconductor being arranged such that its electron incident surface faces said photocathode, and  
       a confining mechanism provided between said photocathode and said electron incident surface of said semiconductor device so as to confine a spread of the photoelectrons from said photocathode, said confining mechanism having an opening for passing through the photoelectrons from said photocathode toward said electron incident surface,  
       wherein said opening of said confining mechanism has a maximum inner diameter not greater than a minimum outer diameter of said incident surface electrode of said semiconductor device, said minimum outer diameter of said incident surface electrode being defined by a minimum distance between intersections where a line passing through a center of said electron incident surface intersects an outer edge of said incident surface electrode.  
     
     
       10. A tube according to claim  9 , further comprising: 
       a container being a hallow member which has a first opening and a second opening opposing maid first opening, said photocathode provided on the first opening side of said container; and  
       a stem provided on the second opening side of said container so as to define a distance between said photocathode and said electron incident surface.  
     
     
       11. A tube according to claim  9 , further comprising an envelope having an opening for supporting said photocathode at a predetermined position and accommodating said confining mechanism such that said semiconductor device is positioned between said confining mechanism and an inner bottom surface of said envelope. 
     
     
       12. A tube according to claim  9 , further comprising: 
       a cathode electrode provided so as to apply a predetermined voltage to said photocathode; and  
       an anode electrode provided between said photocathode and said semiconductor device, said anode electrode having a first surface facing said photocathode, a second surface opposing said first surface, and a through hole extending from said first surface to said second surface; and  
       wherein said confining mechanism includes said anode electrode, and said opening of said confining mechanism is defined by a second-surface-side opening of said through hole of said anode electrode.  
     
     
       13. A tube according to claim  12 , further comprising a mesh electrode provided in the through hole of said anode electrode. 
     
     
       14. A tube according to claim  12 , wherein said anode electrode has a collimator portion which extends from said first surface to said photocathode while surrounding a first-surface-side opening of said through hole of said anode electrode. 
     
     
       15. A tube according to claim  9 , further comprising: 
       a cathode electrode provided so as to apply a predetermined voltage to said photocathode;  
       an anode electrode provided between said photocathode and said semiconductor device, said anode electrode having a through bole for passing through the photoelectrons from said photocathode toward said electron incident surface of said semiconductor device; and  
       a collimator electrode supported by said anode electrode, said collimator electrode having a third surface Lacing said photocathode, a fourth surface opposing said third surface, and a through hole extending from said third surface to said fourth surface; and  
       wherein said confining mechanism includes said collimator electrode, and said opening of said confining mechanism is defined by a fourth-surface-side opening of said through hole of said collimator electrode.  
     
     
       16. A tube according to claim  9 , wherein said semiconductor device has an n-type substrate and a p-type semiconductor layer formed on said n-type semiconductor substrate and having said electron incident surface.